344 research outputs found
Geometrical-induced rectification in two-dimensional ballistic nanodevices
The paper demonstrates that a two-dimensional ballistic nanodevice in which
the electron gas satisfies either the Schroodinger equation (as in quantum
wells in common semiconductor heterostructures) or the Dirac equation (as in
graphene) is able to rectify an electric signal if the device has a non-uniform
cross section, for instance a taper configuration. No p-n junctions or
dissimilar electrodes are necessary for rectification
Problem Identification and Decomposition within the Requirements Generation Process
Only recently has the real importance of the requirements generation process and its requisite activities been recognized. That importance is underscored by the evolving partitions and refinements of the once all-encompassing (and somewhat miss-named) Requirements Analysis phase of the software development lifecycle. Continuing along that evolutionary line, we propose an additional refinement to the requirements generation model that focuses on problem identification and its decomposition into an associated set of user needs that drive the requirements generation process. Problem identification stresses the importance of recognizing and identifying the difference between a perceived state of the system and the desired one. We mention pre- and post-conditions that help identify and bound the problem and then present some methods and techniques that assist in refining that boundary and also in recognizing essential characteristics of the problem. We continue by presenting a process by which the identified problem and its characteristics are decomposed and translated into a set of user needs that provide the basis for the solution description, i.e, the set of requirements. Finally, to place problem identification and decomposition in perspective, we present them within the framework of the Requirements Generation Model
Graphene-like metallic-on-silicon field effect transistor
In this manuscript, we present a field effect transistor with a channel
consisting of a two-dimensional electron gas located at the interface between
an ultrathin metallic film of Ni and a p-type Si(111) substrate. We have
demonstrated that the two-dimensional electron gas channel is modulated by the
gate voltage. The dependence of the drain current on the drain voltage has no
saturation region, similar to a field effect transistor based on graphene.
However, the transport in this transistor is not ambipolar, as in graphene, but
unipolar
Botox in periodontics - Exploring new avenues
From a periodontal point of view, various factors contribute to facial aesthetics. In the recent past, studies have revealed that excessive gingival display is a factor that influences an individualâ smile line. Some literature exists to support that more than excessive gingival display of more than 3mm is considered unaesthetic and termed a âgummy smileâ (GS). The prevalence of 'gummy smileâ has been 10% and to be more common in females. Gingival hyperplasia altered passive eruption, vertical maxillary excess, and upper-lip hypermobility can all result in excessive gingival display when a patient smile.To select the correct treatment protocol, accurate diagnosis is essential. Various techniques have been used to treat gummy smile which includes surgical and non-surgical methods. Recently a non-surgical method using Botulinum toxin gained popularity considering that the method is minimally invasive
Reactions of Rhenium and Manganese Carbonyl Complexes with 1,8-bis(diphenylphosphino)naphthalene: Ligand Chelation, CâH and CâP bond-cleavage Reactions
Reaction of [Re2(CO)8(MeCN)2] with 1,8-bis(diphenylphosphino)naphthalene (dppn) afforded three mono-rhenium complexes fac-[Re(CO)3(Îș1:η1-PPh2C10H6)(PPh2H)] (1), fac-[Re(CO)3{Îș1:Îș1:η1-(O)PPh2C10H6(O)PPh(C6H4)}] (2) and fac-[ReCl(CO)3(Îș2-PPh2C10H6PPh2)] (3). Compounds 1â3 are formed by ReâRe bond cleavage and PâC and CâH bond activation of the dppn ligand. Each of these three complexes have three CO groups arranged in facial fashion. Compound 1 contains a chelating cyclometalated diphenylnaphthylphosphine ligand and a terminally coordinated PPh2H ligand. Compound 2 consists of an orthometalated dppn-dioxide ligand coordinated in a Îș1:Îș1:η1-fashion via both the oxygen atoms and ortho-carbon atom of one of the phenyl rings. Compound 3 consists of an unchanged chelating dppn ligand and a terminal Cl ligand. Treatment of [Mn2(CO)8(MeCN)2] with a slight excess of dppn in refluxing toluene at 72 °C, gave the previously reported [Mn2(CO)8(ÎŒ-PPh2)2] (4), formed by cleavage of CâP bonds, and the new compound fac-[MnCl(CO)3(Îș2-PPh2C10H6PPh2)] (5), which has an unaltered chelating dppn and a terminal Cl ligand. In sharp contrast, reaction of [Mn2(CO)8(MeCN)2] with slight excess of dppn at room temperature yielded the dimanganese [Mn2(CO)9{Îș1-PPh2(C10H7)}] (6) in which the diphenylnaphthylphosphine ligand, formed by facile cleavage of one of the PâC bonds, is axially coordinated to one Mn atom. Compound 6 was also obtained from the reaction of [Mn2(CO)9(MeCN)] with dppn at room temperature. The XRD structures of complexes 1â3, 5, 6 are reported
Direct Measurement of Pyroelectric and Electrocaloric Effects in Thin Films
An understanding of polarization-heat interactions in pyroelectric and electrocaloric thin-film materials requires that the electrothermal response is reliably characterized. While most work, particularly in electrocalorics, has relied on indirect measurement protocols, here we report a direct technique for measuring both pyroelectric and electrocaloric effects in epitaxial ferroelectric thin films. We demonstrate an electrothermal test platform where localized high-frequency (approximately 1 kHz) periodic heating and highly sensitive thin-film resistance thermometry allow the direct measurement of pyrocurrents (<10 pA) and electrocaloric temperature changes (<2 mK) using the â2-omegaâ and an adapted â3-omegaâ technique, respectively. Frequency-domain, phase-sensitive detection permits the extraction of the pyrocurrent from the total current, which is often convoluted by thermally-stimulated currents. The wide-frequency-range measurements employed in this study further show the effect of secondary contributions to pyroelectricity due to the mechanical constraints of the substrate. Similarly, measurement of the electrocaloric effect on the same device in the frequency domain (at approximately 100 kHz) allows for the decoupling of Joule heating from the electrocaloric effect. Using one-dimensional, analytical heat-transport models, the transient temperature profile of the heterostructure is characterized to extract pyroelectric and electrocaloric coefficients
Local shell-to-shell energy transfer via nonlocal Interactions in fluid turbulence
In this paper we analytically compute the strength of nonlinear interactions
in a triad, and the energy exchanges between wavenumber shells in
incompressible fluid turbulence. The computation has been done using
first-order perturbative field theory. In three dimension, magnitude of triad
interactions is large for nonlocal triads, and small for local triads. However,
the shell-to-shell energy transfer rate is found to be local and forward. This
result is due to the fact that the nonlocal triads occupy much less Fourier
space volume than the local ones. The analytical results on three-dimensional
shell-to-shell energy transfer match with their numerical counterparts. In
two-dimensional turbulence, the energy transfer rates to the near-by shells are
forward, but to the distant shells are backward; the cumulative effect is an
inverse cascade of energy.Comment: 10 pages, Revtex
Large-Eddy Simulations of Fluid and Magnetohydrodynamic Turbulence Using Renormalized Parameters
In this paper a procedure for large-eddy simulation (LES) has been devised
for fluid and magnetohydrodynamic turbulence in Fourier space using the
renormalized parameters. The parameters calculated using field theory have been
taken from recent papers by Verma [Phys. Rev. E, 2001; Phys. Plasmas, 2001]. We
have carried out LES on grid. These results match quite well with direct
numerical simulations of . We show that proper choice of parameter is
necessary in LES.Comment: 12 pages, 4 figures: Proper figures inserte
Epstein Barr Virus-positive large T-cell lymphoma presenting as acute appendicitis 17 years after cadaveric renal transplant: a case report
<p>Abstract</p> <p>Introduction</p> <p>The majority of post-transplant lymphoproliferative disorders in renal transplant patients are of the B-cell phenotype, while the T-cell phenotype is rare. We report a case of Epstein Barr Virus-positive, T-cell lymphoma in a renal transplant patient, presenting unusually as acute appendicitis.</p> <p>Case presentation</p> <p>A 45-year-old Hispanic male renal transplant patient presented with right-side abdominal pain 17 years after transplant. The laboratory studies were unremarkable. Laparoscopic exploration showed an inflamed appendix so a laparoscopic appendectomy was performed. Pathology of the appendix showed large cells positive for CD3, CD56 and Epstein Barr Virus-encoded RNA staining, and negative for CD20 and CD30. The tissue tested positive for T-cell receptor gene rearrangement by polymerase chain reaction analysis. Treatment management involved reduction of immunosuppression and initiation of chemotherapy with cisplatin, etoposide, gemcitabine, and solumedrol followed by cyclophosphamide, hydroxydaunorubicin, vincristine and prednisone). He recovered and the allo-grafted kidney is fully functional.</p> <p>Conclusion</p> <p>We report a rare case of post-renal transplant large T-cell lymphoma, with an unusual presentation of acute appendicitis and Epstein Barr Virus-positivity, which responded well to chemotherapy.</p
Perception Is Reality: quality metrics in pancreas surgery â a Central Pancreas Consortium (CPC) analysis of 1399 patients
Several groups have defined pancreatic surgery quality metrics that identify centers delivering quality care. Although these metrics are perceived to be associated with good outcomes, their relationship with actual outcomes has not been established
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